Filter out trouble

chemists at the Indian Institute of Technology (iit), Chennai, have developed a nanoparticle-based technique to remove pesticides from drinking water. The feat is noteworthy, for exposure to pesticides can trigger genetic mutations and neurological disorders. The method was developed by A Sreekumaran Nair and T Pradeep from iit's Department of Chemistry and the Regional Sophisticated Instrumentation Centre respectively. It exploits the unique tendency of gold and silver nanoparticles to adsorb traces of the chemicals.

During their experiments, the scientists used gold particles with a diameter of 10 to 20 nanometres (nm) and silver nanoparticles with a diameter of 60 to 80 nm. The particles were capped with a chemical called citrate (in other words, they were mixed in a diluted solution of the chemical using the reduction process); thereafter, they were put into water tainted with endosulfan, malathion or chlorpyrifos pesticides.

A change in the colour of the nanoparticles indicated the adsorption of the pesticides; for instance, the colour of gold particles changed from intense red wine to shades of blue when they adsorbed endosulfan. The change is due to the binding of the pesticides with the particles and the subsequent aggregation of the latter. The colour change varies, depending on the amount and type of pesticides.

To verify the laboratory results in the field, the scientists loaded the nanoparticles onto columns used in water filters available in the market. Thereafter, they passed water tainted with chlorpyrifos (concentration: one part per million) through the column. When the water was tested using the gas chromatography method, no traces of the pesticide were detected, the scientists claim.

They made yet another discovery